Method of and means for melting and refining metals



prix 28, w3. A. B. KINZEL 2,3 87

METHOD OF AND MEANS FOR MELTING AND REFINING METALS Filed April 25, 19542 Shee'ts-Shee'rI 2 ixw 1 V f2' I Hr *1 f/.Z Z6 f IZ f2 f 2 V2 (ze |-r ll i I l 1 lul-l. Il Il l ll m /4 lNvEN-roR /7 AUGUSTUS BKWNZEL;

l Y BY ,5j ATTORNEY dii Patented lApr. 28, 1936 UNITED STATES amarsiMETHQD 0F AND MEANS FOR. mlb

AND REFINING METALS Augustus B. Kinzel, Douglaston, N. Y., assigner, bymesne assignments, to Union @arbide @arbon Corporation, a corporation ofNew Yorh Application dp t5, liti, Se No. 'lttt t fliaimr.. lill. ttt-52) 'fthe present invention relates to metal melting and/or refiningfurnaces, d more particularly' to methods of 'and means for constructingand operating such furnaces in a more economical manner.

an object of this invention is to simplify the construction, operationand control of metallurgical furnaces, and to incrse the number of heatsor charges which may be melted and/or rehned by such furnaces in a givenunit of time.

.a further object of the present invention is to provide methods of andmeans for edectively applying the principle of voxygen-enriched aircombustion to metallurgical furnaces.

.it still further object of this invention is to provide a method of andmeans for utilizing the pressure crea by the expansion of compressedoxygen-enriched gases to vaporize or atomlze liquid fuels.

lit has been lrnown heretofore that advantages such as more rapidmelting, quiclrer rening, and more direct temperature control in openhearth and other metallurgical furnaces would ensue from higher flametemperatures. There arel several recognized methods of obtaining high detemperatures. One of these is to increase the temperature of the airused. for combustion by recuperating, 1n so-called regenerators, theheat of the waste gases. Another method consists in increasing theoxygen content of the combustion atmosphere in the usualtype ofend-port-hred open hearth furnace. The ports are inclined downward at aslight angle so as to direct the name on the slag or bath. This resultsin producing a slightly higher temperature on the slag than on the roof,but in this type of furnace the considerably higher temperatures whichare desirable cannot be practically and commercially achieved becausethey would result in premature roof failure.v Still another method ofobtaining higher name temperatures involves the use of ports or bers inthe roof of the furnace, the name being impinged substantially at aright angleto 4and upon the bath or slag surface. This produces aslightly higher temperature at the surface of the metal or slag andincreases the temperature differential between the roof and the bath.However, in itself,lthe increase in temperature thus obtained is notsufficiently great and has not proved to be practical due to the greatdilculties involved in bringing hot air for combustion into roof ports.These difficulties relate not only to the complexity of the necessaryvalve mechanism and ducts but also interfere with the cooling of theroof which melts prematurely, so that the ultimate object is notachieved to the desired degree.

Iri'hus, due to the above-stated limitations of furnace construction andmethods of operation, it has notbeen feasible heretofore to increase thetemperature of combustion beyond the point atwhich it is now used inpractice, and no feasible and practical method of obtaining thepotential advantages of oxygen-enriched air has been successfullyachieved.

.in accordance with this invention, the abovementioned disadvantagesinherent in the construction and operation of metallurgical furnaces maybe overcome by combining cold-air firing through the roof with the useof oxygen-enriched air and with other features described hereinafter. Inthis manner, the roof of the furnace is inept cool and is notdetrimentally adected by the high temperature of the fuel-oxygen name.At the same time, in accordance with this invention, the gas how in thefurnace is so regulated by the proper location of the end ports that acomparatively quiet gas zone is continuously liept in contact with theroof, thus further increasing the temperature gradient between the metalbath and the roof. rihis results in a method of operation in which allthe advantages of high temperaturecombustion are achieved, in which thetemperature of the roof is maintained as in normal operation, and inwhich the reversing valves (which are generally unsatisfactory onaccount of the losses of gases leaking directly into the chimney), andthe multiplicity of ducts and other equipment usually necessary for hotair ring through the roof, are eliminated. Furthermore, the constructionand use of heat regenerators is avoided and substantial savings in thecost of construction of furnaces are therefore edected.

Experiments have shown that an enrichment of air from the atmospheric 20per cent oxygen content to about 27 per cent oxygen contentr is sufcientto furnish an extra flame temperature of the same order as obtained bythe preheating in the usual open hearth regenerators, of ordinaryatmospheric air.

The principles of this invention will now be described with particularreference to the accompanying drawings in which:

Figure 1 represents, in a schematic manner, an embodiment of thisinvention in which the principles thereof are applied to a metal meltingand refining furnace;

Figure 2 shows schematically a section along line 'Ll-f of Figure l;

Figure 3 represents a schematic top plan view of a part of the furnaceshown in Figure 1; and

iid

Figure 4 shows, in more detail, a longitudinal sectionithrough theburner shown in Figure 2.'

Referring to the drawings, the furnace shown comprises a bottom orhearth I0 and an arcuate top or roof Il constructed of suitablerefractory materials capable oi withstanding temperatures above themelting point of the metals to be melted and/or refined in the furnace.In the roof ii there are provided a plurality of burners such as shownschematically at I2, and in more detail in Figure 4. Each of saidburners comprises an inner concentric tubular chamber I3 which is formedby and between a central core Ill and a surrounding tube i5; the chamberi3 is connected to a central gas supply passage i6, as shown, and itslower or left-hand portion terminates in an annular discharge orificeill having a small cross-sectional area. Ilfhe gas passage I6 isconnected to a gas supply line 26 which leads to a source ofoxygen-enriched air under pressure, as shown schematically at 29. Thewall I5 of the inner tubular chamber iii is surrounded substantiallyconcentrically by another tube or wall 2l" forming a narrowcircumferential chamber or passage between the outside of tube l5 andthe inner surface of tube 2l'. The tube 2'I is connected, as shown at2i, to a line 28 which leads to a suitable source or liquid fuel underpressure, shown schematically at 48. Liquid fuel tank 48 is connected tothe oxygen gas storage tank 29 through a tank 6i filled with Water. Thepurpose oi this water tank which is arranged in such a manner that itswater level is below the lowest level ofthe fuel tank, is to transmitthe pressure prevailing in container 2@ to the fuel tank 48 withoutthere being any physical contact between the highly compressedoxygen-enriched gas and the liquid fuel. Preferably the pressure in thewater and liquid fuel containers is given a value below the pressure ofthe oxygen-enriched gas, for example, by the interposition of a suitablepressure reducing valve such as shown at 62.

The oxygen-enriched gas which is contained in the vessel 29 preferablyhas an oxygen concentration greater than that of the atmospheric air. Inaccordance with one embodiment of the invention, use is made ofatmospheric air having an oxygen concentration of about 27% or more.

In accordance with a modiiication of this invention there may beprovided, in addition to the container 29 for storing an oxygen-enrichedgas under pressure, a vessel adapted to hold and vaporize liquefiedoxygen-enriched gases. Such a vessel is show n at 3U. This vessel 30contains voxygen-enriched air in the liquid phase, and is adapted toconvert this liquid oxygen-enriched gas into the gaseous phase havingany desired substantially constant pressure, for use both for increasingthe temperature of combustion of the fuel and for Vaporizing oratomizing the liquid fuel. This may be accomplished by providingsuitable means for vaporizing the liqueed gas and for controlling thepressure of the resulting gas. In' order to control the temperature ofthe liquid oxygen-enriched gas and the rate of its evaporation, thecontainer 30 comprises an inner vessel 3| for holding the liquefied gas,and is substantially completely surrounded by the insulating material32. An outer jacket or envelope 33 is provided for protecting andsupporting the insulation 32. Thc inner vessel 3l is constructed towithstand any desired maximum pressure and is provided with suitablefilling means comprising a conduit 34 disposed in the the bottom of thevessel and thus conducts the liquefied gas to a heating coil 3l whichmay be heated electrically or in any other suitable manner and whichvaporizes and heats the gas discharged from conduit 36. The heated gasis then conducted through conduit 38 back into the inner container toeiiect thermal contact with the stored liquefied gas through the wallsof the portion of the conduit 38 which is submerged in the liquefiedgas. In passing through this portion of conduit 38, the superheat of thegaseous oxygen-enriched gas passing therethrough is substantially alltransferred to the stored liquefied gas, thus producing the vaporizationoi a. desired portion of the stored liquefied gas, whereby the pressureof the gas within the vessel and in conduits and apparatus in directconnection therewith is increased to any desired Value.

The discharge portion of conduit 3S conducts the gas to a second heatexchange coil 39 where it is i'eheated to any desired temperature. Theamount oi' heat applied to the heat exchange coils all and 39 may becontrolled in any conventional manner. From the heating coil 3@ a con'-duit il@ conducts the gas to the inlet of an auto matic premurecontrolling means 4i which maintains the discharge pressure of the gasdelivered through conduit d2 at a substantially constant desired valuewhen the inlet pressure is at a varying higher value. The conduit 42 isjoined to the conduit 2G which conducts gas at a desired substantiailyconstant pressure to the burners I2. A conduit lill, disposed in theupper portion of the vessel it@ and connecting with the space above thestored liquid gas conducts gas when desired to the inlet of an automaticback pressure Valve 45. This valve permits no gas to pass until thepressure of the gas in conduit 4I reaches or exceeds a desired setvalue.. When this set pressure is exceeded, gas is permitted to flowthrough the conduit 4d to a second automatic pressure reducing valvelll?. The reducing valve 41 discharges through conduit 26 and maintainsany desired discharge pressure of the gas therein at a substantiallyconstant value.

The operation of the heating system described is substantially asfollows:

Assuming the pressure of the reducing valve 4l' to be set for a Value ofsay 150 lbs. per square inch, and the heat exchange coils or rheostats3l and 39 to be set for a corresponding heat value, oxygen-enriched gashaving this pressure is conducted to the conduit 26 and to theburnersI2, and issues from the annular orifice I'I thereof in the form of aspray of very high velocity. The pressure of the liquid fuel beingpreferably adjusted to a value less than that of the oxygenenriched gas,say to about to 100 lbs. per square inch, liquid fuel is caused to flow,by virtue of the pressure exerted upon it through conduit 52, valve 62,tanks 6I and 48,-into supply line 28, and issues from the orifice ofburners I2 in a direction substantially at a right angle to thedirection of ow of the compressed oxygen-enriched gas. Owing to theimpact of the highly compressed gas upon the liquid fuel, the fuel isvaporized and the vaporized fuel and the gas of combustion areintimately mixed in the combustion chamber. This mixture of fuel andoxygen-enriched gas burns with the production of a long flame whosetemperature may be of the order of 2000 C. or more. The zone of maximumtemperature occurs substantialiy at the end points of the flame, that isat the point of contact of the flame with the metal or metal bath uponthe hearth of the furnace. v

By causing a plurality of high-temperature llames to impinge upon thecharge, during and after the melting thereof, it is possible to oxidizethe various impurities contained in the charge considerably more rapidlythan is possible with the use of lower llame temperatures. Aconsiderable shortening of the melting and refining operation is thusobtained, which results in an increased number of heats per unit oftime, and in considerable savings in overhead expenses. The method ofproviding a plurality of long and hot yflames which are directeddownward upon the metal or metal bath together with the design and thelocation of the end ports, permits the accumulation of an inert layer ofgas directly underneath the roof, and enables a furnace construction inwhich the roof is at a considerably greater height from the surface ofthe bath than would be possible otherwise. Thus the roof may bemaintained cool very eiectively, and consequently its useful life isincreased several fold.

Although the advantages and applications of this invention are notlimited to the use of liquid fuel, since gaseous fuel has other obviousadvantages, when using fuel oil instead of gas fuel. no generators arerequired for the production of the oil fuel. In view of the hightemperature of the oxygen flame, the length of time required for meltingand refining a heat or charge is considerably reduced. and noregenerators are needed for recuperating the heat content of theescaping waste gases. Consequently, the cost of constructing andoperating a furnace in accordance with this invention, as well as thecost of maintaining such a furnace in repair and operation, isconsiderably reduced.

Furthermore, owing to the complete vaporization or atomization of theliquid fuel, use may be made of the heavier and more economical types offuel oil which heretofore have been considered unsatisfactory as fueloil on account of the diiiiculties experienced in their vaporization oratomization. g

By increasing the oxygen to nitrogen ratio from the normal ratio of l to4 to approximately 1 to 3,

or l to 2, the proportion of the nitrogen in the waste gases andconsequently the volume ofthe waste gases is considerably decreased,thus cor'- respondinglyreducing the amount of heat which is abstractedfrom the furnace chamber in the form of waste gases. Furthermore, ifdesired, in any particular case, the amount of heat wasted may bereduced still further by utilizing at least one portion of the escapingflue gases for heating steam boilers. and using the resulting steam forthe operation of steam engines, or for the operation of theoxygen-concentrating apparatus, or for any other purpose. Thisutilization of the waste gases may be particularly advisable in allcases in which the temperature of the waste gases is sufficiently highto warrant any of these methods of operation.

What I claim is:

1. Method of producing high temperatureswithin a combustion chamberwhich comprises projecting an ignited finely divided jet, consisting ofa mixture of fluid fuel and oxygen-enriched air, downward through theroof of said chamber, and maintaining a relatively thick layer ofsubstantially quiescent gas adjacent to the under side of said roof.

2. lA furnace for melting or refining metals and the like whichcomprises a hearth; a roof; sidewalls; means for'projecting an ignitedmixture of fiuid fuel and oxygen-enriched air from one or more points asubstantial distance below said roof downwards onto said hearth; and oneor more ports in said sidewalls for discharging gaseous products ofcombustion, said port or ports being located in a lower portion of saidsidewalls; whereby, a relatively thick layer of substantially quiescentgas is maintained between the roof and the zone of combustion in saidfurnace.

3. A heating system which comprises, in combination with the furnaceclaimed in claim 2, a vessel adapted to hold liquefied oxygen-enrichedair under pressure; a vessel adapted to hold liquid fuel; means fortransmitting pressure from said first-mentioned vessel to saidsecond-mentioned vessel without permitting oxygen-enriched air to entersaid second-mentioned vessel; means for vaporizing the lsaid liquefiedoxygen-enriched air to create said pressure; and one or 'more liquidfuel atomizers and meansI for conducting said liquid fuel and saidvaporized oxygen-enriched air

